1. Field of the Invention
The present invention relates generally to golf balls containing at least one layer made from a thermoset polyurethane or polyurethane-urea composition that is based on a moisture-resistant polyol. More particularly, the composition is produced from a reaction of polyisocyanate with a moisture-resistant polyol and curing agent. The composition may be used to form any layer in the golf ball such as, for example, an outer core, intermediate layer, inner cover, and/or outer cover. The resulting golf ball has desirable playing performance properties including high resiliency, toughness, impact durability, moisture-resistance, and soft feel.
2. Brief Review of the Related Art
Today, multi-piece solid golf balls are popular for several reasons including new manufacturing methods, the availability and cost of raw materials, and the playing performance properties of such balls. For example, three-piece solid golf balls having an inner core and outer cover with an intermediate layer disposed there between are commonly used by both professional and recreational golfers. Many multi-piece balls are designed to have an optimum combination of playing properties. Particularly, such balls are designed to have high durability and resiliency as well as a soft feel. The durability and toughness of the ball protects it from being cut, torn, and otherwise damaged. Balls having a high resiliency tend to reach a high velocity when struck by a golf club. As a result, the ball tends to travel a greater distance which is particularly important for driver shots off the tee. Meanwhile, the soft feel of the ball provides the player with a more pleasant sensation when he/she strikes the ball with the club. The player senses more control over the ball as the club face makes impact. The soft feel of the ball's cover allows players to place a spin on the ball and better control its flight pattern which is particularly important for approach shots near the green.
In conventional multi-piece golf balls, the inner core is made commonly of a rubber material such as natural and synthetic rubbers, styrene butadiene, polybutadiene, poly(cis-isoprene), poly(trans-isoprene), or highly neutralized acid copolymers. Often, the intermediate layer is made of an olefin-based ionomer resin that imparts some hardness to the ball. These ionomer acid copolymers contain inter-chain ionic bonding and are generally made of an α-olefin such as ethylene and a vinyl comonomer having an acid group such as methacrylic, acrylic acid, or maleic acid. Metal ions such as sodium, lithium, zinc, and magnesium are used to neutralize the acid groups in the copolymer. Commercially available olefin-based copolymer ionomer resins are used in different industries and include numerous resins sold under the trademarks, Surlyn® (available from DuPont) and Escor® and Iotek® (available from ExxonMobil), Amplify IO® (available from Dow Chemical) and Clarix® (available from A. Schulman). Olefin-based copolymer ionomer resins are available in various grades and identified based on the type of base resin, molecular weight, and type of metal ion, amount of acid, degree of neutralization, additives, and other properties. Finally, the outer cover of conventional golf balls are made from a variety of materials including olefin-based copolymer ionomers, polyamides, polyesters, and thermoplastic and thermoset polyurethane and polyurea elastomers.
In recent years, there has been substantial interest in using thermoset and thermoplastic polyurethanes to make cover layers for the golf balls. Polyurethane golf ball covers are of particular interest because they can be formulated to provide the golf ball with high resiliency and durability as well as a soft feel. Basically, polyurethane compositions contain urethane linkages formed by reacting an isocyanate group (—N═C═O) with a hydroxyl group (OH). Polyurethanes are produced by the reaction of a polyisocyanate with a polyol in the presence of a catalyst and other additives. The chain length of the polyurethane prepolymer is extended by reacting it with a hydroxyl-terminated curing agent. Hybrid compositions containing urethane and urea linkages also may be produced. For example, a polyurethane/urea hybrid composition may be produced when polyurethane prepolymer is reacted with an amine-terminated curing agent.
Golf balls made with polyurethane and polyurea materials are generally described in the patent literature, for example, U.S. Pat. Nos. 5,334,673; 5,484,870; 6,476,176; 6,506,851; 6,867,279; 6,958,379; 6,960,630; 6,964,621; 7,041,769; 7,105,623; 7,131,915; and 7,186,777. As discussed above, in general, isocyanate compounds with two or more functional groups are reacted with polyols to form the polyurethane compositions. There are various known methods for making thermoplastic polyurethanes. For example, Meltzer et al., U.S. Patent Application Publication No. US 2009/0192262 describes a specific method for making hydrophobic thermoplastic polyurethanes. According to the '262 Publication, a polyol, a polyisocyanate, and a linear diol chain extender containing 5 carbon atoms or 7 to 12 carbon atoms are required as the reactants. There is no disclosure of isocyanate or polyol compounds containing acidic or ionic moieties. The '262 Publication discloses that the thermoplastic polyurethane compositions may be used for over-molding soft grips onto tools and kitchen utensils, and in adhesives and protective coatings.
Although many conventional golf balls containing polyurethane components or layers have good mechanical and playing properties, there is a continuing need for improved polyurethane golf balls. The improved golf balls should have high resiliency, impact durability, and toughness as well as features that make the ball easy to play with, particularly a pleasant feel, softness, and the like. The present invention provides methods for making such golf balls and the resultant balls. The present invention relates to multi-layered golf balls made from a composition comprising a thermoset polyurethane or polyurethane-urea. The composition may be used to form any layer in the golf ball structure such as, for example, outer core, intermediate layer, inner cover, and/or outer cover. The golf balls made of the compositions of this invention are highly resilient and have good impact durability and toughness. Moreover, the ball has a soft feel and optimum playing performance properties.